Various rotational mold apparatus have been suggested for distributing thermoplastic particles against a heated mold surface to form a thin shell article conforming to the shape of the casting surface. Examples of such apparatus are shown in U.S. Pat. Nos. 3,222,725, 4,167,382 and 4,767,299. While suitable for their intended purpose such prior art mold apparatus require full removal of covers or top shells.
Likewise, various prior art rotational mold apparatus have been proposed with a pivotal member which operates during a molding cycle. Such apparatus however does not include a support for a concave shell mold forming one part of a closed casting system for depositing thermoplastic particles onto a heated mold surface for forming a thin shell article with a shape conformed to that of the casting surface. Examples of such mold apparatus are set forth in U.S. Pat. Nos. 2,060,121 which discloses a centrifuge for extracting water from bricks; 2,230,778 which discloses a tile press and cutter with a hinged cover; 3,844,702 which discloses a centrifugal mold for forming dentures; 4,008,990 which discloses a mold apparatus with two mold halves for forming polyurethane foam products; 4,411,531 discloses an extruder having a pivotal member which is provided for ease of cleaning a ram section of the apparatus. The arrangements do not disclose or suggest a shell mold apparatus in which a bottom shell mold is carried on a spindle for rotation on a spider and wherein a moveable cover carrier is operated to position either a cover or a top concave heated shell mold part in a closed position on the bottom shell mold during rotational molding and in an opened position on the spindle during cleaning of the shell mold surfaces so as to reduce the mold cycle time.